Ink reservoir for ball point pen



Jan. 17, 1956 F. F. BOYLE INK RESERVOIR FOR BALL POINT PEN Filed Jan. 6,1951 INVENTOR. F. BOYLE FARNHAM States Patent om INK RESERVOIR FOR BALLPOINT PEN Farnham F. Boyle, St. Louis, Mo., assignor, by mesneassignments, to Ritepoint Pen and Pencil Company, St. Louis, Mo., acorporation of Missouri Application January 6, 1951, Serial No. 204,754

2 Claims. (Cl. 120-424 This invention pertains to the structure of ballpoint pens and more particularly to an ink reservoir therefor, which mayform part of a refill unit.

An object of this invention is to provide a refill unit having an inkreservoir in the form of an open end tube, such tube being of amplevolume and at the same time having provision for preventing leakage ofthe ink from the open end.

In accordance with this invention, the ink reservoir is in the form of arigid tube preferably of plastic. This tube is formed at one end with ahead adapted to receive the ball point tip. Above this head the tube hasa bore of non-circular cross section. In the illustrated embodiment,this bore has a plurality of internal ribs extending therealong. Theseribs increase the perimeter of the bore and thereby the extent of thesurface to which the ink may cling, without seriously reducing thevolume thereof. Since the ink tends to cling to the wall of the tube,this increase in the surface to which it may cling serves to prevent itfrom leaking out of the open end of the tube.

A preferred embodiment of the invention is illustrated in theaccompanying drawing, in which:

Fig. 1 is a longitudinal section of an ink tube embodying thisinvention;

Fig. 2 is a section on line 2-2 of Fig. l; and

Fig. 3 is a detail section of the open end of the tube before reforming.

In the embodiment illustrated, an ink reservoir tube 1 is provided,sized to fit into the barrel of the pen in the usual manner. This tubeis of rigid material, preferably of plastic and is formed with a head 2at its lower end adapted to receive a ball point tip 3. This assemblyprovides a refill unit for the pen. The bore of the tube 1 isnon-circular in cross section as may be seen from Fig. 2. This sectionmay have various shapes, the one shown being formed by an outer circularbore 4 provided with a plurality of internal ribs 5. Between the ribs 5recesses or channels 6 are formed. As shown in Fig. l, the ribs 5 extendalong a major portion of the length of the tube 1 except for an enlargedcircular portion 7 provided to receive the tip 3. While in the drawingthe tube is shown with six internal ribs, any other number may be usedand the general form of the outer limit of the bore may be ofnon-circular form.

The ribs 5 terminate short of the upper end of the tube as indicated at8 so as to leave the upper end open for the insertion of a plug 9 intothe bore of the tube. This plug may be of any suitable material. It hasbeen found desirable to make the same of resilient material, such asfelt.

In the embodiment shown, the plug 9 is originally circular in outlineand of a diameter somewhat larger than the inner diameter of the ribs 5.The plug is then pushed into the bore of the tube so as to be placedunder compression at the ribs 5, the intermediate portions bulging intothe spaces 6 as indicated in Fig. 2.

-ttented J Before insertion of the plug 9, the tube is filled with inkat a suitable viscosity and a rod 10 is also placed in the tube. Thisrod may be simply a length of wire of suitable diameter and is arrangedso as to be imbedded in the ink in the tube. After inserting the chargeof ink and the rod 10, the plug 9 is inserted and thereafter the upperend of the tube 1 is heated and swaged over as shown at 11 so as toclose the upper end of the tube except for an opening 12 to admitatmospheric pressure.

The ink used to chargethe tube is preferably of a relatively highviscosity so that by its internal friction and its adhesion to the innerwall of the tube and the surface of the ribs 5, its flow along the tubeis retarded sufiiciently to prevent leakage of the ink out of theopening 12. The plug 9 which is spaced a substantial distance from theopening 12 assists in preventing the flow of ink toward said opening.The spacing of the plug 9 from the opening 12 should be sutficient toprevent capillary creepage of the ink along the tube from reaching saidopening.

The rod 12 is loose in the tube 1 so that it may move about as theposition of the pen is changed in the handling thereof. Accordingly, themovements of the pen in handling will cause the rod to move bothlengthwise and laterally in the bore of the tube. This movement providesan agitating action by the rod 10 which tends to break up any airbubbles which may form in the ink and assist in maintaining a uniformflow of ink to the ball tip 3.

It will be seen, therefore, that this invention provides a structurewhereby an ink reservoir of relatively large ink capacity is provided,while at the same time the tendency for such a large volume of ink toleak from the open end of the tube is prevented, namely by the adhesionof ink to the internal surface of the tube, which surface is increasedin extent over that of an ordinary circular tube by provision of theribs. Since the adhesion of the ink is active throughout these surfaces,it will be seen that such adhesion particularly as assisted by the plug9 will prevent a flow of ink sufiicient to run out at the opening 12. Atthe same time, the continual feed of ink to the ball point is assured byprovision of the agitator 10 to break up air bubbles and provideagitation sufiicient to encourage movement of the ink toward the tip asit is used up in Writing.

Various changes may be made in the details of construction, within thescope of the appended claims, without departing from the spirit of thisinvention. Parts of the invention may be used without the whole andimprovements may be added while retaining some or all of the advantagesof the invention.

I claim:

1. In a ball point pen, an ink reservoir comprising a rigid tube havingan internal tubular bore provided with an opening in the upper portionthereof, said bore having a plurality of substantially straight,radially inwardly projecting, axial ribs, said ribs being uniformlyspaced from each other around the periphery of the bore so that thespace therebetween will constitute straight axial grooves extendingalong a major portion of the length of said tube, and a plug engagingsaid ribs in said tube in the upper portion thereof thereby closing amajor portion of said opening and forming in combination with said tubea plurality of air passages along said grooves thereby allowing air toenter into said tube below said plug.

2. In a ball point pen, an elongated ink reservoir comprising a tubehaving a substantially uniform bore formed with a plurality oflongitudinally extending and alternately disposed substantially straightaxially extending, uniformly spaced ribs and grooves extendingtherealong for a major portion of the length of said tube,

3 7 said tube having .a ,headithereon at one ,end thereof adapted toreceive, a ball point tip, said tube having an opening at the other endthereof adapted to admit air to said tube, and a resilient porous plugin said tube spaced from said opening, said plug contacting said ribsbut not the bottoms of said grooves thereby forming a plurality of airpassages along said grooves to admit air at ali times to said tubebetween said plug and said ball point tip.

References Cited in the *file of this patent UNITED STATES PATENTSStewart Feb. '3, 1881

